National Public Radio (NPR) in a brief news item, this morning
reported results of a new experiment to establish the period
of the circadian cycle in humans.
Since initial experiments in Germany, it has been held that
the natural rate when not entrained by circadian cues, was
around 25 hours.
With new insights into photo entrainment, the experimental
environment standardized the room lighting ( formerly under experimental
subjects' control) and then the experimental results
closely followed those for animals: a period of 24 hours and a
few minutes.
Their results easily explain earlier long period resiults on
the basis of self-stretching of the period with extended lighting for
reading, etc.
The new study was itself impeachable on the basis of the age of the
subjects who apparently were selected on the basis of their (older)
ages.